1. Field of the Invention
The invention relates to a light-diffusing structure with excellent light diffusing effect and a light guide plate having enhanced luminous uniformity and light utilization efficiency.
2. Description of the Related Art
Generally, a linear light source, such as a cold cathode fluorescent lamp (CCFL) is not favorable for hand-held electronic devices due to its bulkiness. Instead, a point light source is typically used in a hand-held electronic device like a mobile phone and serves as the side light source for an LCD panel incorporated therein. FIG. 1 shows a schematic diagram illustrating a conventional backlight module 100. As shown in FIG. 1, a point light source like a light emitting diode (LED) 104 is next to a light-receiving surface 102a of a light guide plate 102, and its bottom surface 102c is provided with prismatic structures consisting of V-shaped grooves 106. As shown in FIG. 2, since the relationship between the light radiating angle and energy of a point light source follows Lambert's emission law, when an LCD panel uses the LED 104 as an side light source and a prism sheet (not shown) for guiding the light from the LED 104 toward the normal of a light-emitting surface 102b of the light guide plate 102, the distribution of bright bands 110 and dark bands 112 with sharp contrast always appear in a localized area near the light-receiving surface 102a. This tends to result in uneven brightness of the light guide plate 102.
Therefore, another design of light-diffusing structures is disclosed to solve the above problem. For example, as shown in FIG. 3, a plurality of triangular prism-like structures are arranged on the light-receiving surface 122 to form V-shaped structures 120. Alternatively, as shown in FIG. 4, a plurality of cylindrical prism-like structures are arranged on the light-receiving surface 132 to form arc-shaped structures 130. The light diffusing effect provided by these light guiding structures may obviate the uneven brightness of the light guide plate 102 and enhance light utilization efficiency. However, the conventional V-shaped structure 120 or arc-shaped structure 130 has limited light diffusing capability. Thus, even these light guiding structures are provided, the areas of bright/dark bands spread on the light guide plate 102 are still considerable. Thus, the brightness distribution is still not uniform and the areas of the effective section that provides uniform surface illumination of the light guide plate 102 cannot be further increased.